`ust`, `ust2`, `msc`, and `msc2` are unsigned, so their difference is
still unsigned. The `>0` assert could never fail.
Fix this by simplifying the test to compare the pairs of values directly.

Fixes: 5d9f5df0 ("Implementation of eglGetSyncValuesCHROMIUM extension.")
Fixes: ee218f27 ("Re-land eglGetSyncValuesCHROMIUM extension.")
Signed-off-by: Eric Engestrom <eric.engestrom@imgtec.com>
Change-Id: I0b19d786720f545c846640d48c30a83a1d001396
Reviewed-on: https://chromium-review.googlesource.com/500189Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>